Single use inertia absorbing device

ABSTRACT

An inertia absorbing device is disclosed to absorb relatively large amounts of inertial energy on a one shot or single use basis. Energy is absorbed by elongating or stretching a thermoplastic structure, such as nylon yarn. One example of an end use would be an energy absorbing system for automobile bumpers to prevent low speed (5-10 mph) collision damage. Nylon yarn is attached to pins between a movable bumper mount and the automobile frame, to be stretched on collision.

Unite States Patent Carter 14 1 Sept. 26, 1972 [541 SINGLE USE INERTIAABSORBING 2,837,176 6/1958 Dropkin ..188/1 C DEVICE 2,933,127 4/1960Brewster ..188/1 C X [72] Inventor: John Ed Carter, Columbia, SC.3,074,760 1/1963 Hodgekln ..188/1 C UX [73] Assignee: Allied ChemicalCorporation, New FOREIGN PATENTS OR APPLICATIONS York, NY. 297,84412/1929 Great Britain ..293/89 [22] Flled: 1970 Primary Examiner-DuaneA. Reger [21] Appl. No.: 91,705 Attorney-Richard A. Anderson 52 US. (:1..293/101, 188/1 0, 293/87, [57] ABSTRACT 293/88, 293/89 An inertiaabsorbing device is disclosed to absorb rela- 51 1m. 01. .LFl6f 7/12tively large amounts of inertial energy on a one shot or [58] Field ofSearch ..188/1 c; 293/70, 72, 89, 87, Single use basisgy is absorbed yelongating or 33/138,101, 1 3 stretching a thermoplastic structure, suchas nylon yarn. One example of an end use would be an energy 56 v R f C-d absorbing system for/automobile bumpers to prevent I 1 e erences I elow speed (5-10 mph) collision damage. Nylon yarn is UNITED STATESPATENTS attached to pins between a movable bumper mount '1 b t h d 11'-1,540,945 6/1925 Miller ..293/89 g m frame e S 6 2,465,936 3/1949Schultz ..'.188/1 C UX 2,578,903 12/1951 Smith ..188/1 C 10 Claims, 1Drawing Figure 2'\ a Q a y N x rmmznsm m2 3.694.019

INVENTOR. John E Carter ATTORNEY SINGLE USE INERTIA ABSORBING DEVICEBACKGROUND OF THE INVENTION SUMMARY OF THE INVENTION The basic idea ofthis invention is to use the energy necessary to align the molecules incertain synthetic thermoplastic materials from a random orientation toan orientation along an axis of elongation. This energy is necessary toovercome intermolecular friction, i.e., the resistance of the moleculesto slip past each other to become realigned along an axis rather than inrandom orientation. The material for this invention must be capable ofbeing permanently highly elongated. Broadly, the invention is a singleuse inertial absorbing device utilizing a length of energy absorbingnon-elastic material, which is drawable to a permanent elongation,attached at one end to a fixed support and attached at the other end toa movable member. The movable member is mounted to contact a movingobject so that upon contact the inertia of the moving object is absorbedby stretching the energy absorbing non-elastic material between thefixed support and the movable member. This can be accomplished bywinding a skein of undrawn yarn around the pins mounted on the fixedsupport and movable members or by mounting multiple layers of undrawnfilm wound around the pins of the fixed support and movable member. Thematerial for this invention can be any energy absorbing nonelasticmaterial which is capable of becoming permanently elongated. Many of theman-made or synthetic polymers have molecules arranged in a randomlyoriented crystalline structure suspended in a matrix of amorphousmolecules as first formed during manufacture and prior to any molecularorientation caused by drawing or stretching of the polymer. Typical ofsuch drawable, orientable, randomly oriented crystalline and amorphousmolecular materials are the polyamides, polyolefins andpolyvinylchloride. Typical polyamides would be polycaprolactam,polyhexamethylene adipamide and the entire family of polymers preparedby polymerizing a dicarboxylic acid with a diamine or self-polymerizingmonocarboxylicmonoamino acids or their derivatives such as lactams.Typical polyolefins would be polyethylene or polypropylene. In a fewapplications, even polymers like the polyesters could possibly be usedif sufficient heat were present to allow drawability of the polymer. Thephysical embodiment of the polymer may be as undrawn multifilament yarn,undrawn monofilament, undrawn strands or undrawn film. The amount ofenergy absorption by the polymer material can easily be controlled bythe quantity of yarn, monofilament strands or filmattached to the fixedand movable elements. In other words, the amount of cross sectionsubject to elongation can be varied by changing the number of wrapsaround pins or the number of pieces of material between attaching means.By yarn is meant filaments having a diameter of from about 0.0001 to0.02 inch. By strands is meant large filaments having a diameter of fromabout 0.02 to a diameter which would shear rather than draw, possibly upto 5 inches.

A more specific summary of this invention would be a single use or oneshot energy absorbing device for an automobile bumper to prevent lowspeed collision damage wherein a skein of undrawn strands or multiplelayers of undrawn film of a material such as polyamide attached at oneend to the automobile frame and attached at the other end to a slidablebumper mounting member so that upon low speed collision the yarn or filmis stretched between the slidable bumper mounting member and the frameto absorb energy of the colli- SIOII.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an isometric view of aspecific embodiment for use between an automobile bumper and frame.

PREFERRED EMBODIMENTS A preferred embodiment of this invention is shownin FIG. 1. Strands l of nylon or polyolefin are wound skein fashionaround metal pins 2 which are attached to automobile bumper 3 and frame6. A box section sup port 5 with shear pin 4 is used to support theassembly. The shear pin is designed to shear at l to 2 miles per hour.The quantity of energy absorption by the strands after the shear pinshears is easily controlled by the changing quantity of polyamide orpolyolefin, i.e., number of strands and can be easily adjusted forvehicle weight, desired travel and velocity. Approximate force toelongate polycaproamide is 2,600 psi so that nominal amounts of undrawnpolymer can provide substantial absorption. Polyamide has the propertyof being capable of elongation to 700 percent before rupture and does sowith constant energy absorption rate. A system of 4 inches in totalcross sectional area will stop a vehicle weighing 4,000 pounds from 5mph in 3% inches. This is well within the design esthetics for bumperprotrusion, travel distance, and would result in no damage other than tothe bumper and the thermoplastic skeins, which are simple andinexpensive to replace.

EXAMPLE In the laboratory, a 10 pound weight was arrested by apolycaproamide structure from a freefall at 5.0 mph in 4.0 and 4.75inches in two trials. The structure required 20 pounds to elongate,2,600 psi tension. It is calculated that this test run horizontally,i.e., pendulum arrest, would require 3.5 inches since the accelerationof gravity is avoided on horizontal basis.

Iclaim:

l. A single use energy absorbing device for an automobile bumper toprevent low speed collision damage comprising a length of energyabsorbing, non-elastic material which is cold drawable to a permanentelongation,

attached at one end to the automobile frame and attached at the otherend to a slidable bumper mounting member secured with a shear pin in anopen-ended box-type support, said shear pin being securely seated insaid slidable member and passing through a mated opening in said support1 so that upon low speed collision said material is stretched betweensaid slidable bumper mounting member and said frame to absorb the energyof said collision.

2. The device of claim 1 wherein said material is a skein of undrawnyarn.

3 The device of claim 1 wherein said material is a multiple layer ofundrawn film. I

4. The device of claim 2 wherein said yarn is polya- 9. The device ofclaim 1 wherein the material is a strand.

10. The device of claim 9 wherein said strand is polyamide.

1. A single use energy absorbing device for an automobile bumper toprevent low speed collision damage comprising a length of energyabsorbing, non-elastic material which is cold drawable to a permanentelongation, attached at one end to the automobile frame and attached atthe other end to a slidable bumper mounting member secured with a shearpin in an openended box-type support, said shear pin being securelyseated in said slidable member and passing through a mated opening insaid support so that upon low speed collision said material is stretchedbetween said slidable bumper mounting member and said frame to absorbthe energy of said collision.
 2. The device of claim 1 wherein saidmaterial is a skein of undrawn yarn. 3 The device of claim 1 whereInsaid material is a multiple layer of undrawn film.
 4. The device ofclaim 2 wherein said yarn is polyamide.
 5. The device of claim 2 whereinsaid yarn is polypropylene.
 6. The device of claim 3 wherein said filmis polyethylene.
 7. The device of claim 4 wherein said polyamide ispolycaproamide.
 8. The device of claim 3 wherein said film ispolypropylene.
 9. The device of claim 1 wherein the material is astrand.
 10. The device of claim 9 wherein said strand is polyamide.